Thanks for your help guys. I've made a temporary fix by ID-ing the cables, and running a temp power feed. So working now....BUT....Turn signals still work even when ignition is off ! But at least a fix of sorts.
It seems that the 4WD switch on top of the manual shifter is linked to this fuse, and keeps blowing. I need to look into this as a separate issue.
Does anyone know where I can find a circuit for this part of the electrics ? A lot of the advertised manuals seem to have 'Engine Electrics' only, and nothing about lights, turn signals etc.